Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$181.53	8.492%	$196.9455	$196.95	$196.95	$196.90
Purchase #2	$232.56	4.506%	$243.0392	$243.04	$243.05	$243.00
Purchase #3	$19.58	4.204%	$20.4031	$20.40	$20.40	$20.40
Purchase #4	$122.69	7.725%	$132.1678	$132.17	$132.15	$132.20
Purchase #5	$35.59	13.626%	$40.4395	$40.44	$40.45	$40.40
Purchase #6	$12.25	5.704%	$12.9487	$12.95	$12.95	$12.90
Purchase #7	$179.26	10.662%	$198.3727	$198.37	$198.35	$198.40
7 purchase totals =	$783.46		$844.3165	$844.32	$844.30	$844.20